Low disengage speed fan clutch

Abstract

A clutch includes an input element with an engaged input shaft and clutch plate rotatable in concert. The clutch plate has an annular portion with a clutch plate set of lands and grooves mating with a housing set of lands and grooves to define a shear zone space. A cover is included as part of the housing and engages the body and includes a reservoir. A pump plate is captured between the cover and the body separating out a working chamber generally within the body and includes a pump port. The pump port includes an outer extreme edge that is substantially in line with the outer surface of the clutch plate. A valve port in the pump plate is positioned near the radial outside of the reservoir. A control arm normally closes the valve port and is movable to open the valve port. When the valve port is closed, fluid carried in the working chamber moves radially outward under centrifugal force and is forced through the pump port under operation of a wiper due to relative rotation between the clutch plate and the pump plate so that substantially all of the fluid is pumped out of the working chamber and a high slip speed is established between the housing and the clutch plate. A rotating peripheral accumulator is defined between the depleted surface of the clutch plate and the annular step of the body that accommodates fluid inertia and provides volumetric compensation for fluid pressurization and compression caused by an externally applied torque change.

I claim: 
     
       1. A clutch comprising: an input element including an input shaft with a clutch plate engaged with the input shaft to rotate in concert therewith, the clutch plate having an annular disk portion with a clutch plate set of lands and grooves, with an outer surface formed radially outside the clutch plate set of lands and grooves and a depleted surface formed adjacent the outer surface;   a housing including a body supported on the input shaft by a bearing with a body set of lands and grooves mating with the clutch plate set of lands and grooves, with a shear zone space defined between the clutch plate set of lands and grooves and the body set of lands and grooves, wherein the body includes an annular step formed radially outwardly from the body set of lands and grooves, and wherein a cover is included as part of the housing and is engaged with the body and includes a reservoir;   a pump plate captured between the cover and the body separating out a working chamber, the pump plate including a valve port and a pump port positioned further radially outward in the pump plate than the valve port, with a wiper positioned adjacent the pump port, wherein the pump port includes an outer extreme edge that is substantially in line with the outer surface of the clutch plate and wherein the valve port is positioned near a radial outside of the reservoir; and   a control arm normally closing the valve port and being movable to open the valve port, wherein when the valve port is closed a fluid carried in the working chamber moves radially outward under centrifugal force and is forced through the pump port under operation of the wiper due to relative rotation between the clutch plate and the pump plate so that substantially all of the fluid is pumped out of the working chamber and a slip speed between the housing and the clutch plate of approximately 4000 revolutions per minute is achieved, wherein a rotating peripheral accumulator is defined between the depleted surface of the clutch plate and the annular step of the body that accommodates fluid inertia and provides volumetric compensation for fluid pressurization and compression caused by an externally applied torque change.   
     
     
       2. A clutch according to claim 1 wherein an annular space is defined between the outer surface of the clutch plate and an adjacent surface of the body and wherein volumetric size of the rotating peripheral accumulator is larger than volumetric size of the annular space. 
     
     
       3. A clutch comprising: an input element including an input shaft with a clutch plate engaged with the input shaft to rotate in concert therewith, the clutch plate having an annular disk portion supported by a series of spokes with openings between the spokes, wherein the clutch plate includes a clutch plate set of lands and grooves, with an outer surface formed radially outside the clutch plate set of lands and grooves and a depleted surface formed adjacent the outer surface;   a housing including a body supported on the input shaft by a bearing with a body set of lands and grooves mating with the clutch plate set of lands and grooves, with a shear zone space defined between the clutch plate set of lands and grooves and the body set of lands and grooves, wherein the body includes an annular step formed radially outwardly from the body set of lands and grooves;   a cover included as part of the housing and engaged with the body, the cover including a reservoir and a channel extending generally radially outward from the reservoir to a chamber in the cover;   a pump plate captured between the cover and the body separating out a working chamber generally within the body, the pump plate including a valve port and a pump port positioned further radially outward in the pump plate than the valve port, with a wiper positioned adjacent the pump port, wherein the pump port includes an outer extreme edge that is in line with the outer surface of the clutch plate and wherein the valve port is positioned near a radial outside of the reservoir; and   a control arm normally closing the valve port and being movable to open the valve port, wherein when the valve port is closed a fluid carried in the working chamber moves radially outward under centrifugal force and is forced through the pump port under operation of the wiper due to relative rotation between the clutch plate and the pump plate, wherein the wiper develops a high pressure zone on the working chamber side of the pump port so that substantially all of the fluid is pumped out of the working chamber through the pump port and into the chamber in the cover and is forced through the chamber and the channel to the reservoir, wherein a slip speed between the housing and the clutch plate of approximately over 4000 revolutions per minute is achieved, wherein a rotating peripheral accumulator is defined between the depleted surface of the clutch plate and the annular step of the body that accommodates fluid inertia and provides volumetric compensation for fluid pressurization and compression caused by an externally applied torque change, wherein when the valve port is opened, fluid moves from the reservoir into the working chamber through the valve port under centrifugal force, and in the working chamber fluid moves through the openings between the spokes of the clutch plate and into the shear zone space to transfer increased levels of torque from the input element to the housing.   
     
     
       4. A clutch according to claim 3 wherein an annular space is defined between the outer surface of the clutch plate and an adjacent surface of the body and wherein volumetric size of the rotating peripheral accumulator is larger than volumetric size of the annular space. 
     
     
       5. A clutch comprising: an input element including an input shaft with a clutch plate engaged with the input shaft to rotate in concert therewith, the clutch plate having an annular disk portion supported by a series of spokes with openings between the spokes, wherein the clutch plate includes a clutch plate set of lands and grooves, with an outer surface formed radially outside the clutch plate set of lands and grooves and a depleted surface formed adjacent the outer surface, wherein the clutch plate includes a radially extending dispersion channel slicing completely through the clutch plate set of lands and grooves;   a housing including a body supported on the input shaft by a bearing with a body set of lands and grooves mating with the clutch plate set of lands and grooves, with a shear zone space defined between the clutch plate set of lands and grooves and the body set of lands and grooves, wherein the body includes an annular step formed radially outwardly from the body set of lands and grooves, wherein the body includes a radially directed expulsion channel slicing completely through the body set of lands and grooves;   a cover included as part of the housing and engaged with the body, the cover including a reservoir and a channel extending generally radially outward from the reservoir to a chamber in the cover;   a pump plate captured between the cover and the body separating out a working chamber generally within the body, the pump plate including a valve port and a pump port positioned further radially outward in the pump plate than the valve port, with a wiper positioned adjacent the pump port, wherein the pump port includes an outer extreme edge that is in line with the outer surface of the clutch plate and wherein the valve port is positioned near a radial outside of the reservoir; and   a control arm normally closing the valve port and being movable to open the valve port, wherein when the valve port is closed a fluid carried in the working chamber moves radially outward under centrifugal force and is forced through the pump port under operation of the wiper due to relative rotation between the clutch plate and the pump plate, wherein the wiper develops a high pressure zone on the working chamber side of the pump port so that substantially all of the fluid is pumped out of the working chamber through the pump port and into the chamber in the cover and is forced through the channel to the reservoir, wherein a slip speed between the housing and the clutch plate of approximately over 4000 revolutions per minute is achieved, wherein a rotating peripheral accumulator is defined between the depleted surface of the clutch plate and the annular step of the body that accommodates fluid inertia and provides volumetric compensation for fluid pressurization and compression caused by an externally applied torque change, wherein when the valve port is opened, fluid moves from the reservoir into the working chamber through the valve port under centrifugal force, and in the working chamber fluid moves through the openings between the spokes of the clutch plate and into the shear zone space to transfer increased levels of torque from the input element to the housing wherein fluid is facilitated in moving through the shear zone space by fluid dispersion effected through registry between the dispersion channel in the clutch plate and the expulsion channel in the body.   
     
     
       6. A clutch according to claim 5 wherein an annular space is defined between the outer surface of the clutch plate and an adjacent surface of the body and wherein volumetric size of the rotating peripheral accumulator is larger than volumetric size of the annular space. 
     
     
       7. A clutch for driving a fan at low disengage speeds and at relatively higher engage speeds wherein the fan is subjected to variable torque loads comprising: an input element including an input shaft with a clutch plate engaged with the input shaft to rotate in concert therewith, the clutch plate having an annular disk portion supported by a series of spokes with openings between the spokes, wherein the clutch plate includes a clutch plate set of lands and grooves, with a radially outward facing outer surface formed radially outside the clutch plate set of lands and grooves and a depleted surface formed adjacent the outer surface, wherein the clutch plate includes a radially extending dispersion channel slicing completely through the clutch plate set of lands and grooves and having a V-shaped cross section;   a housing including a body supported on the input shaft by a bearing with a body set of lands and grooves mating with the clutch plate set of lands and grooves, with a shear zone space defined between the clutch plate set of lands and grooves and the body set of lands and grooves, wherein the body includes a grooved annular step formed radially outwardly from the body set of lands and grooves and a radially inward facing surface adjacent the grooved annular step, wherein the body includes a radially directed expulsion channel slicing completely through the body set of lands and grooves;   a cover included as part of the housing and engaged with the body, the cover including a reservoir and a channel extending generally radially outward from the reservoir to a chamber in the cover;   a pump plate captured between the cover and the body separating out a working chamber generally within the body, the pump plate including a valve port and a pump port positioned further radially outward in the pump plate than the valve port, with a wiper positioned adjacent the pump port, wherein the pump port includes an outer extreme edge that is in line with the outer surface of the clutch plate and wherein the valve port is positioned generally radially outside of the reservoir; and   a control arm normally closing the valve port and being movable to open the valve port, wherein when the valve port is closed a fluid carried in the working chamber moves radially outward under centrifugal force and is forced through the pump port under operation of the wiper due to relative rotation between the clutch plate and the pump plate, wherein the wiper develops a high pressure zone on the working chamber side of the pump port so that substantially all of the fluid is pumped out of the working chamber through the pump port and into the chamber in the cover and is forced through the channel to the reservoir, wherein a slip speed between the housing and the clutch plate of approximately over 4000 revolutions per minute is achieved, wherein a rotating peripheral accumulator is defined between the depleted surface of the clutch plate and the grooved annular step of the body that accommodates fluid inertia and provides volumetric compensation for fluid pressurization and compression caused by the variable torque loads, wherein an annular space is defined between the outer surface of the clutch plate and the radially inward facing surface of the body and wherein volumetric size of the rotating peripheral accumulator is large relative to volumetric size of the annular space, wherein when the valve port is opened, fluid moves from the reservoir into the working chamber through the valve port under centrifugal force, and in the working chamber fluid moves through the openings between the spokes of the clutch plate and into the shear zone space to transfer increased levels of torque from the input element to the housing wherein fluid is facilitated in moving through the shear zone space by fluid dispersion effected through registry between the dispersion channel in the clutch plate and the expulsion channel in the body.   
     
     
       8. A clutch according to claim 7 wherein the clutch plate includes six dispersion channels and the body includes three expulsion channels so that registry between the dispersion channels and the expulsion channels results in as many as 72,000 fluid dispersions per minute.